The dwellers in the soil 



67 



experiments yourselves. Divide a little rich garden 

 soil into two parts and bake one in the kitchen oven 

 on a patty tin. Pour a little milk into each of two 

 small flasks, stop up with cotton wool (see Fig. 26) 

 and boil for a few minutes very carefully so that the 

 milk does not boil over, then allow to cool. Next care- 

 fully take out the stopper from one of the flasks and 

 drop in a little of the baked soil, label the flask "baked 

 soil" and put back the stopper. Into the other flask 



Fig. 25. 

 Fresh soil turns milk bad, but baked soil does not 



drop a little of the untouched soil and label it; leave 

 both flasks in a warm place till the next day. Carefully 

 jopen the stoppers and smell the milk: the baked soil 

 has done nothing and the milk smells perfectly sweet ; 

 the unbaked soil, on the other hand, has made the milk 

 bad and it smells like cheese. If you have a good 

 microscope you can go further : look at a drop of the 

 liquid from each flask and you find in each case the 



